Install oinkmaster than register to snort.org it should give you an id-key that looks like this:g34fa5gdt65678jhsgfs34 , you will use it to download snort rules it gives instruction on setting up a cron job that regulary as soon an update comes for the snort rules it will download them and set them up for you.Sorry if i don't give you more details but i only set it once and never stopped working it's the best,oinkmaster.